crypto: sun8i-ce - pass task descriptor to cipher prepare/unprepare

To remove some duplicated code, directly pass 'struct skcipher_request' and
'struct ce_task' pointers to sun8i_ce_cipher_{prepare,unprepare}.

Signed-off-by: Ovidiu Panait <ovidiu.panait.oss@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>